Connective Tissue Includes the most abundant and widely distributed tissues Functions: Binds body tissues together Supports the body Provides protection

Connective Tissue Characteristics Most tissue types are well vascularized (bone, adipose, reticular, areolar) Some have poor blood supply or are avascular (cartilage, ligaments, tendons) matrix Non-living material that surrounds living cells

Extracellular Matrix (cont.) Two main elements of matrix: 1. Ground substance – mostly water along with adhesion proteins and polysaccharide molecules 2. Fibers (3) – made by the cells Collagen fibers (strongest) Elastic fibers Reticular fibers (delicate)

Connective Tissue Types Bone (osseous tissue) Composed of: Bone cells-(osteocyte) in lacunae (cavities) Hard matrix of calcium salts Large numbers of collagen fibers Used to protect and support the body Figure 3.19a

Connective Tissue Types Hyaline cartilage Most common cartilage Composed of: Abundant collagen fibers Rubbery matrix Cells - chondrocyte Examples: entire fetal skeleton, ends of long bones Figure 3.19b

Connective Tissue Types Elastic cartilage Provides elasticity Example: ear, wall of aorta

Connective Tissue Types Fibrocartilage Highly compressible Example: cushion-like discs between vertebrae Figure 3.19c

Connective Tissue Types Dense connective tissue Main matrix element is collagen fibers Cells are fibroblasts Examples Tendon – attach muscle to bone Ligaments – attach bone to bone Figure 3.19d

Connective Tissue Types Areolar (loose) connective tissue Most widely distributed connective tissue Soft, pliable tissue Contains all fiber types Ex. packs most of our organs Figure 3.19e

Connective Tissue Types Adipose tissue (fat) Matrix is an areolar tissue Storage, cushions, protects, insulates Examples? Figure 3.19f

Connective Tissue Types Reticular connective tissue Delicate network of fibers Examples: Lymph nodes Spleen Bone marrow Figure 3.19g

Connective Tissue Types Blood Blood cells surrounded by fluid matrix (plasma) RBC’s, WBC’s and platelets Figure 3.19h

Muscle Tissue Types (3) 1. Skeletal muscle voluntary striated have more than one nucleus (multinucleate) Figure 3.20a

Muscle Tissue Types 2. Cardiac muscle Found only in the heart (involuntary) Cells attached to each other at intercalated disks striated One nucleus per cell Figure 3.20b

Muscle Tissue Types 3. Smooth muscle Involuntary No visible striations (smooth) One nucleus per cell Ex. Lines hollow organs, blood vessels, reproductive tracts Figure 3.20c

Nervous Tissue Neurons and nerve support cells send impulses to other areas of the body Figure 3.21

Tissue Repair (2 ways) 1. Regeneration 2. Fibrosis (scar tissue) Replacement of destroyed tissue by the same kind of cells 2. Fibrosis (scar tissue) Repair by dense fibrous connective tissue (scar tissue) Tissues that are replaced largely with scar tissue: Cardiac muscle Nervous tissue within the brain and spinal cord Joints (knee and elbow)

Developmental Aspects of Tissue With old age there is a decrease in mass and viability in most tissues (atrophy) Atrophy will also occur when tissues (muscles) are not used Most prominent in muscles